My invention relates to impact attenuation devices, and more particularly to an energy absorbing system employable for reducing the severity of vehicular collisions, especially of the type involving a fast moving motor vehicle and a highway service vehicle engaged in highway maintenance and repair operations, from the standpoint of limiting the extent of injury suffered by people and the damage done to equipment as a consequence of such collisions.
It has long been known in the prior art to employ accident preventive measures in an effort to prevent and/or reduce the damage incurred by both humans and property resulting from vehicular collisions occuring on the Nation's major highways as well as its local roads. Such accident preventive measures may be classifiable for purposes of this discussion into two basic categories; namely, warning devices designed to be operative to forestall the occurrence of a vehicular collision, and protective devices designed to afford protection to both persons and property in the event of the occurrence of a vehicular collision.
By way of illustration, the category of warning devices is intended to include such items as conventional traffic signs and traffic signals, emergency signs and signals displayed to warn of the temporary existence of a dangerous situation, etc. Protective devices fall into two classes, i.e., those embodied in a vehicle as part of the construction thereof, and those which are viewed as being separate from the construction of the vehicle, irrespective of whether the latter are subsequently affixed in some manner to the exterior of the vehicle. Examples of protective devices, which fall within the first class, are such things as padded dashboards, seat belts, etc. In the second class are to be found such things as various types of safety barriers designed to afford protection in the event of a vehicular collision between a moving vehicle and an immovable object, or between a moving vehicle and another moving object. The present invention relates to a protective device of the type falling within the second class thereof as defined hereinabove.
Referring now in more detail to the aforesaid second class of protective devices, the nature of the immovable objects to which reference is had here are such things as bridge piers, light stanchions, guardrails, signposts, concrete walls and abutments, etc. Typically, an attempt is made to provide protection against a moving vehicle striking such immovable objects by positioning a stationary traffic safety barrier in proximity to the immovable object and so that it lies along the path, which the moving vehicle would most likely follow if it were to strike the immovable object. Such stationary traffic safety barriers are most often intended to function in the manner of an impact attenuation device; namely, to attenuate the forces produced as a result of the impact of the moving vehicle striking the immovable object, and thereby reduce the severity of the vehicular collision as relates to the extent of injury suffered by the individuals riding in the moving vehicle and the amount of property damage incurred by both the moving vehicle and the immovable object.
For ease of reference during the following discussion, such stationary traffic safety barriers will hereinafter be referred to as stationary energy absorbing barriers. One of the earliest attempts made at providing a stationary energy absorbing barrier involved the employment of a system composed of fifty-five gallon drums. Patterns were cut into the lids of the drums to reduce the crushing strength of the system, i.e., to provide the system with the desired controlled crushing characteristics.
The successful implementation of this fifty-five gallon drum modular crash cushion system prompted a study of the feasibility of employing other possible forms of stationary energy absorbing barriers. In this regard, corrugated steel pipe was found to have favorable characteristics when it was statically crush tested. Moreover, the availability of corrugated steel pipe having a wide range of thicknesses and diameter dimensions made it feasible to employ a polymodular design in which the physical characteristics of the stationary energy absorbing barrier could be varied on a row to row basis.
Examples of other forms of stationary energy absorbing barriers, which are known to exist in the prior art, include the following: a hydro cushion cell barrier composed of an array of water filled plastic cells operable such that upon impact, the water is ejected through orifices in the top of the cells at a controlled rate; a barrier formed by an array of nine to seventeen sand-filled frangible plastic barrels, which is characterized by its versatile applicability; a U-shaped tubular guardrail energy absorbing barrier that absorbs energy by means of the motion of supporting telescopic tubes such that upon impact, the impact forces are transmitted axially to arms, which contain many stainless steel torus elements that are squeezed between two cylindrical tubes; a barrier in the form of a vehicle arresting system that is composed of a steel entrapping net positioned across a roadway, and which is particularly applicable for use in proximity to locations such as road dead ends, ferry landings, highway medians at bridge overpasses, etc.; a lightweight cellular concrete crash cushion barrier constructed of easily frangible vermiculite concrete with vertical voids wherein the vertical voids contribute to the controlled crushing characteristics of the barrier; for use primarily as part of a guardrail system, a barrier based on a fragmenting tube concept, which was originally developed for use in planned lunar landing modules, and in which energy is absorbed by forcing a thick walled aluminum tube over a flared die, resulting in the shedding of the tube into small segments; and lastly, an energy absorbing barrier particularly applicable for use as part of a guardrail system and in which thick walled steel rings are utilized.
In addition to the potential for danger posed by immovable objects, which are to be found located along the Nation's major highways and along its local roads, there is another situation, which has the potential for danger that one often encounters while traveling along these same major highways and local roads. Reference is had here to the hazardous condition often posed by the presence on such highways and roads of men and equipment engaged in highway maintenance and repair operations. There is a need to protect such personnel and equipment from being struck by an errant moving vehicle. The stationary energy absorbing barriers which have been described herein previously, are generally found to be unsuited to provide the desired degree of protection to the personnel and equipment while involved in conducting highway and road maintenance operations. To provide this needed protection, what is required is an energy absorbing barrier which is portable in nature in contrast to the stationary nature of the energy absorbing barriers to which reference has previously been had herein.
Although most of the attention of the prior art heretodate has been directed towards providing various kinds of stationary energy absorbing barriers, there is known to exist in the prior art at least two different types of portable energy absorbing barriers, the latter more commonly being viewed as comprising a system. One such portable energy absorbing system is in the form of a hydro-cell system and consists of five rows of thirteen polyvinyl chloride plastic cells enveloped in a corset-like membrane. The entire unit is mounted on a metal platform, which is designed to be attached to the rear of a highway service vehicle. Each cell contains approximately three and one-half gallons of a water-calcium chloride solution. The latter solution functions to provide the system with the desired controlled crushing characteristics. The hydro-cell portable energy absorbing system, although being portable in nature and relatively easy to install has been found to suffer from the major disadvantage that it cannot simultaneously satisfy the energy absorption and minimum stopping distance, i.e., deceleration requirements for moving vehicles impacting thereagainst at speeds in excess of thirty miles per hour.
The other known form of portable energy absorbing system is the modular crash cushion system, which is composed of thirty steel drums, i.e., ten rows with three drums per row. The thirty drums rest on a trailer, which is designed to be attached to a highway service vehicle at five points to provide the required degree of horizontal and vertical stability during impact. The principal disadvantage of the modular crash cushion portable energy absorbing system stems from the fact that it is nineteen and one-half feet long. As a consequence, because of the need to maintain a rigid interconnection between the trailer and the towing service vehicle at all times, this system has been shown to suffer from severe wear limitations as concerns both the trailer on which the drums rest and the service vehicle which tows the trailer. In addition, because of its relatively long length, this system has proven to be unsuitable for use on the hilly and curved sections of highways and roads, which are found to exist in many areas of the country.
In summary, a need has been demonstrated for a new and improved portable energy absorbing system, suitable particularly for use in such applications as providing protection against being struck by an errant moving vehicle to men and equipment engaged in highway and road maintenance and/or repair operations. There are a number of characteristics, which it is desired that such a new and improved portable energy absorbing system should possess. Namely, the system should be capable of absorbing most of the energy dissipated in a high speed collision between a moving vehicle and a highway service vehicle. Moreover, the system should be capable of absorbing this energy in such a way that the accelerations and the acceleration rates to which the moving vehicle and the highway service vehicle are subjected as a consequence of a collision therebetween are within the guidelines specified by the Federal Highway Administration. Also, the use of the system should be unrestricted by the existence of hilly and/or curved sections of highways and roads. Furthermore, the system should be inexpensive to construct and employ. Lastly, the system should be suseptible to quick and inexpensive repair following its involvement in a vehicular collision.